Method for drilling underwater well



Dec. 13, 1966 N. E. MONTGOMERY METHOD FOR DRILLING UNDERWATER WELL Original Filed Oct. 9, 1963 2 Sheets-Sheet l 46 251; 50 f 7 r VAR M 3 FIG. I I INVENTOR:

HIS AGENT N. E- MONTGOMERY METHOD FOR DRILLING UNDERWATER WELL Dec. 13, 1966 2 Sheets-Sheet 2 Original Filed Oct. 9, 1965 FIG. 5

FIG. 7

FIG. 6

INVENTORI N. E. MONTGOMERY H 7 5% HJS AGENT United States Patent 5 Claims. (Cl. 166.5)

The present application is a divisional application of copending application Serial No. 315,026, filed October This invention relates to underwater drilling of oil and gas wells and pertains more particularly to methods and apparatus for installing a conductor or a foundation pipe together with an underwater well base structure at an underwater location.

During the recent years, the continued search for oil has resulted in developing methods and apparatus for drilling underwater wells at locations Where the water may range from 100 to 1500 feet or more in depth. In these locations it is customary to position the wellhead assembly at a considerable distance below the surface of the water, preferably on the ocean floor, so that it is not a hazard to the navigation of ships in the area. When drilling a well by one of the presently known methods, a floatable drilling barge or vessel is located over a preselected drill site offshore prior to commencing drilling operations. Alternatively, instead of a floating drill barge, a floating drilling platform may be employed which is provided with a plurality of legs which are extendible down through the water to the ocean fioor to serve as a firm footing for the barge during drilling operations.

One of the most important operations in the drilling of an underwater well is that of starting the well and installing the conductor or foundation pipe in the ocean floor. This operation may be carried out in any one of several ways, two of which are described in US. Patent 2,929,610, which issued March 20, 1960, to H. Stratton, and U.S. Patent 2,891,770, which issued June 23, 1959, to R. P. Bauer et al. In one method a drill bit drills a hole in the ocean floor slightly larger in diameter than the diameter of the well conductor or foundation pipe which is subsequently slipped down along the drill pipe and into the hole during which drilling fluid is pumped down the drill pipe and up the outside of the foundation pipe. In another method, a hole is flushed in the ocean floor for the well conductor or foundation pipe by pumping fluid down the conductor, allowing it to jet out the lower end thereof to wash a hole in the ocean floor into which the conductor pipe is progressively lowered. The conductor pipe is then held in place in the hole until the surrounding earth has had time to settle in around the outside of the pipe and anchor it firmly in the hole.

In certain locations, the above-described methods of starting to drill a well in the ocean floor and positioning a well conductor or foundation pipe therein are unsatisfactory because of the peculiar soil conditions of the ocean floor. In certain locations, the ocean floor is too soft to drill a hole of shallow depth without the earth caving in and filling the hole as fast as it is drilled. Alternatively, if a hole is first washed in the ocean floor while lowering a conductor pipe progressively into the hole, there is insufficient bearing surface or frictional contact between the surrounding earth formation that settles into the hole and the outside of the pipe to permit the pipe to support any substantial weight.

Therefore, where soft or silty ocean floor conditions are encountered, it is desirable to sink a large-diameter well pipe in the ocean floor for say 50 feet or more, which pipe would be outside and surround what is normally 3,201,209 Patented Dec. 13, 1966 the well conductor or foundation pipe. With a drilling vessel positioned at the drilling site and an underwater well base structure temporarily supported below the operating deck thereof, a normal well conductor pipe, say 20 inches in diameter, could be inserted downwardly through the temporarily supported well base and positioned under the rotary table of the drilling vessel so that drilling operations can be carried out by running the drill stern and bit down through the well support base and conduct-or pipe to the ocean floor. However, in order to be able to first sink a large-diameter well pipe, say 30 inches in diameter, into the ocean floor prior to carrying out drilling operations, it would be necessary to move the well base structure to one side on the drilling vessel where it would not be in the way. This would be necessary as a 30 inch diameter Well pipe could not be run through the central opening of the well base designed to support a 20 inch foundation pipe.

The equipment employed in drilling underwater wells is tremendous in size and weight and difficult to handle in offshore locations, especially on a floating drilling vessel. For example, one underwater wellhead support base, including the guide system rigidly secured thereto, is 16 feet in diameter, about 30 feet high and weighs 34,000 pounds. When this Well base structure is originally hoisted from an auxiliary barge to a drilling vessel, it is desirable to place it in the position it is to be used so that it does not have to be moved on the drilling vessel from one location to another. It was found to be extremely difficult and time consuming to move a heavy well structure on a drilling vessel.

It is therefore a primary object of the present invention to provide a method and apparatus for starting the drilling of an underwater well whereby a well conductor pipe or foundation pipe together with a well base structure may be installed on a relatively soft ocean bottom in a manner so that substantialweight can be supported from the well base.

A further object of the present invention is to provide a method and apparatus whereby varying sizes of largediameter well pipe or casing adapted to be positioned in a concentric manner in the ocean floor may be lowered from a drilling vessel through a well base structure that is temporarily supported on the vessel.

Another object of the present invention is to provide an apparatus for use as an underwater well base which is designed to allow passage through the base of a largediameter pipe on which the well base subsequently rests.

Still another object of the present invention is to provide a well base apparatus adapted to pass a large-diameter well pipe therethrough and subsequently hang a smaller-diameter string of pipe therefrom and within the large-diameter pipe.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURE 1 is a diagrammatic view illustrating an offshore drilling vessel of the floating type with a stringof pipe depending from the vessel into a well which has been drilled in the ocean floor;

FIGURE 2 is a longitudinal fragmental view, taken partially in cross section, of the auxiliary support deck of the vessel of FIGURE 1 illustrating a drill string with a large-diameter bit extending through the large-diameter central opening in a well base structure;

FIGURE 3 is a longitudinal fragmental view taken partially in cross section of the well base structure of FIGURE 2 with an auxiliary support ring installed in the central opening of the well base;

FIGURE 4 is a longitudinal section taken partially in cross section illustrating a well casing and/or casinghead 3 suspended from and connected to the auxiliary support in the center of the well base structure of FIGURE 3;

FIGURE 5 is a plan view of the well base support structure of FIGURE 2 illustrating the removable auxiliary support base in the center thereof;

FIGURE 6 is a cross section exploded view taken along the line 6-6 of FIGURE 5; and

FIGURE 7 is a cross sectional view taken along the line 7-7 of FIGURE 5.

Referring to FIGURE 1 of the drawing, a drilling vessel, barge or platform 11, of any suitable floating or fioatable type is illustrated as floating on the surface of a body of water 12 while being substantially fixedly positioned over a pre-selected well location by suitable vessel-positioning means well known to the art, or by being anchored to the ocean floor 13 by anchor lines 14 and 15 running to anchors (not shown). Equipment of this type may be used when carrying on well-drilling operations or wellworkover operations in water varying from about 100 to 1500 feet or more in depth. The drilling vessel 11 is equipped with a suitable derrick 16 containing a fall line system 17 which includes a suitable hoist 18, travelling block 19, and suitable hook or other connector means 20 adapted to connect to the top of a large diameter pipe, such as a well pipe, well casing, running pipe string, or drill string 21. The vessel 11 is also provided with other auxiliary equipment needed during well-drilling operations, such for example, as a rotary table 22 positioned on the operating deck, a hinged slip-and-spider assembly, etc. The derrick 16 is positioned over a drilling slot or well which extends vertically through the vessel in a conventional manner. When using the equipment of the present invention, the slot in the vessel 11 may be either centrally located or extend in from one edge. Alternatively, drilling operations may be carried out over the side of the vessel without the use of a slot, as illustrated in FIGURE 1. For example, the drilling vessel 11 may be provided with a deck portion 23 which overhangs the hull of the vessel.

A well base structure 25 is illustrated in FIGURE 1 and 2 as being temporarily supported on the vessel 11, as by being supported on removable arms or deck sections 26 and 27 (FIGURE 2) which may be pivoted to one side, for example, downwardly, when it is desired to lower the well base structure 25 to the ocean floor. Cables or chains 28 and 29 temporarily support the movable deck sections 26 and 27 in place. The laterally-extending wellhead support base 25 is provided with a large-diameter vertical substantially central opening 30 extending therethrough, the opening being of a size to pass therethrough the largest pipe or casing member to be used in the well installation.

The well or wellhead support base 25 may be provided with two or more guide columns or posts 31 and 32. Alternatively, as shown in FIGURE 5, the laterally-extending well base structure 25 may comprise a framework of a plurality of radially-extending I-beams 33 held together with cross-bracing beams 34. The well base structure FIGURE 5 is provided with three main guide columns 35, 36, and 37 arranged at equidistant spaced intervals from the outer line of the well base structure 25. In addition, the well base structure is provided with a pair of auxiliary guide columns 38 and 39.

An auxiliary support base which may be in the form of a ring element 40, having a central opening 41 therethrough, is adapted to be removably secured to the center of the Well base structure 25. As shown in FIGURE 6, the auxiliary base or ring element in the center of the well base 25 (FIGURE 5) has a series of radially and outwardly-extending arms 42 forming, together with bolts 43, connector means for securing the ring element 40 to the I-beams 33 of the well base 25. Bolts 43 are illustrated as suitable connector means although it is to be understood that any other suitable type of connector means may be employed. In the event that bolts 43 (FIGURE 6) are used, it is preferred to adopt the time-saving expedient of welding the nut 44 to the underside of the beam 33. A cross-sectional view showing the arm 42 positioned and secured on the I-beam 33 is shown in FIGURE 7.

The upper edge of the inner wall of the auxiliary base support or ring element 40 forms a landing surface, which may be beveled, to seat thereon an outwardly-extending flange 46 fixedly secured to or formed on a well conductor or foundation pipe 47, as shown in FIGURE 4. The upper end of the well conductor 47 may be provided with one or more grooves 48 in the outer surface thereof for securing a wellhead connector or a running tool (not shown) thereto. Preferably, the auxiliary base or ring element 40 is provided with a plurality of connector means for securing the foundation pipe 47 (FIGURE 4) t0 the ring element 40 which in turn is secured to the well base structure 25. The pipe connect-or means may take the form of a series of latch housings 50 each having a spring-loaded inwardly and radially-extending latch 51, as shown in FIGURE 6. It may be seen that the latches 51 are designed to latch over the flange 46 (FIGURE 4) on the outside of the foundation pipe 47.

In accordance with the method of the present invention, drilling of an underwater well is carried out from a floating vessel provided with well-drilling apparatus including a rotary table adapted to be positioned below suitable hoist apparatus for lowering equipment to the ocean floor while at the same time the welldrilling apparatus is positioned above an auxiliary lower deck for supporting a well base temporarily on the vessel. When the well base 25 is first hoisted off a Work boat used to deliver the well base 25 to the vessel 11, it is hoisted into the position shown in FIGURE 1, and supported temporarily below the fall line system 17 of the derrick 16. In the event that a large-diameter well pipe greater than 24 inches in diameter is to be first installed in the ocean floor, the rotary table 22 is normally removed from the operating deck of the vessel to give an opening sufficiently large to permit the large-diameter pipe to pass therethrough. A large-diameter pipe 55 is lowered by means of a running pipe string down through the central opening 30 (FIGURE 2) in the center of the well support structure 25, and thence downwardly to the ocean floor 13 where it is inserted in any manner well known to the art. For example, it may be forced into the ocean floor by means of applying weight to the top of the large-diameter pipe, as by the use of removable weight cans or by applying pressure to the running pipe string, the use of weight cans being described in copending application Serial No.223,- 36 8, filed September 13, 'l962. At the same time the large-diameter pipe 55 is forced in the ocean floor 13, guide lines 56 and 57 may have been secured to the top of the pipe 55 to aid in subsequently lowering other equipment such as a drill string or pipe string into the well pipe 55. By providing the large central opening 30 (FIGURE 2) through the well base structure 25, weight cans and other large-diameter equipment may readily pass therethrough. After the large-diameter pipe 55 is in place in the ocean with its upper end preferably adjacent to the ocean floor, the diameter of the central opening 30 through the supported well base 25 (FIGURE 2) is reduced by inserting the ring 40 (FIGURE 3) in the opening and securing the arms 42 (FIGURE 6) of the ring element 40 to the I-beams 33 of the well base 25. A largediameter bit 58 is shown in FIGURE 2 at the end of the drill spring 21 prior to inserting the ring element 40 in the central opening 30 of the well base 25. After the ring element 40 has been installed in the well base 25, a smaller-diameter bit would be run down through the central opening 41 of the ring element 40 and down into the pipe 55 in the ocean floor at the end of a drill string in order to continue drilling well 60 to a depth suflicient to receive the well conductor or foundation pipe 47 (FIGURE 4). In the event that the rotary table 22 had been removed while installing the pipe 55, the rotary table 22 would be replaced prior to resuming drilling operations.

When the well 60 had been drilled to the desired depth, the drill string 21 and bit at the bottom thereof would be pulled back to the vessel and the well conductor or fun-dation pipe 47 (FIGURE 4) would be lowered down through the rotary table opening and down through the opening 41 in the ring element 40 until the flange 46 near the top of the conductor pipe was landed on the beveled landing surface 45 (FIGURE 6). As fiange 46 (FIG- URE 4) passes the spring-loaded latches 51 (FIGURE 6) the latches 51 would automatically retract and again snap out over the top of the flange 46, as shown in FIGURE 4. The entire well base and guide structure 25 together with the well conductor 47 are then lowered from the vessel after the retractible deck sections 26 and 27 have been lowered out of the way. Lowering of the well base and conductor to the ocean floor may be accomplished in any manner well known to the art, as by means of a running pipe string connected to the grooves 48 (FIG- URE 4) at the top of the conductor pipe, or by using the guide lines 61 and 62 extending from the well base and upwardly to the vessel at the surface. Prior to lowering the well base into place on top of the large-diameter pipe 55 (FIGURE *1) in the hole, wi-re line cutters may be run down the temporary guide lines 56 and 57 from the vessel to cut them and withdraw them to the vessel.

Thus, it may be seen that the method and apparatus of the present provides for handling large equipment and starting a well at an ofishore location without the necessity of moving heavy equipment around on the vessel.

I claim as my invention:

1. A method of drilling an underwater well from a floating drilling vessel having a retary table opening therein and provided with well-drilling apparatus including a rotary table adapted to the positioned below apparatus for lowering equipment to the ocean floor and above apparatus for supporting a well base on the vessel, said method comprising:

supporting temporarily on said drilling vessel below the lowering apparatus thereof a well base having a largediarneter vertical central opening therethrough,

suspending from the lowering apparatus of said vessel a vertically positioned large-diameter well pipe extending down through the central opening of said supported well base,

lowering said large-diameter well pipe from said vessel and inserting it into the ocean floor so that the up- 6 per end of said pipe is adjacent to the ocean floor, reducing the diameter of the central opening through the supported well base at the vessel,

drilling a hole in the ocean floor through the well pipe positioned therein,

running a string of well casing through the reduced central opening of said well base of said vessel until the lower end of said casing is in said hole and the upper end of said casing is at said supported well base,

connecting said well base to the well casing near the upper end thereof, and

lowering said easing into the hole until the well base connected to said casing is positioned adjacent the top of the well pipe set in the ocean floor.

2. The method of claim 1 wherein said vessel is provided with an operating deck having an opening therein for a rotary table and including the step of suspending and lowering said well pipe through said rotary table opening prior to lowering it through the central opening of said well base.

3. The method of claim 1 wherein the diameter of the central opening through said well base is reduced by inserting a ring element in said opening and securing said ring element in a removable manner to said well base.

4. The method of claim 3 including the steps of installing a rotary table in the rotary table opening of said vessel, extending a drilling string through said rotary table and through the central opening of said supported well "base down into the well pipe set in the ocean floor to drill a hole therein.

5. The method of claim 3 including the step of applying weight to the large-diameter well pipe while inserting it into the ocean floor.

References Cited by the Examiner UNITED STATES PATENTS 2,010,199 8/1935 R-otinoif 6O X 3,063,507 11/1962 ONeill et al. 166-.5 X 3,077,227 2/1963 Haeber 166-.5 3,080,921 3/ 1963 Lacy 166-.5 3,137,348 6/1964 Ahlstone et a1 166-.6 3,159,218 12/1964 Wilde l66.6 3,190,358 6/1965 Johnson et al 166.5 3,191,696 6/1965 Pollard ct a1. 1757 0 CHARLES E. OCONNELL, Primary Examiner.

R. E. FAVREAU, Assistant Examiner. 

1. A METHOD OF DRILLING AN UNDERWATER WELL FROM A FLOATING DRILLING VESSEL HAVING A RETARY TABLE OPENING THEREIN AND PROVIDED WITH WELL-DRILLING APPARATUS INCLUDING A ROTARY ADAPTED TO THE POSITIONED BELOW APPARATUS FOR LOWERING EQUIPMENT TO THE OCEAN FLOOR AND ABOVE APPARATUS FOR SUPPORTING A WELL BASE ON THE VESSEL, SAID METHOD COMPRISING: SUPPORTING TEMPORARILY ON SAID DRILL VESSEL BELOW THE LOWERING APPARATUS THEREOF A WELL BASE HAVING A LARGE-DIAMETER VERTICAL CENTRAL APENING THERETHROUGH, SUSPENDING FROM THE LOWERING APPARATUS OF SAID VESSEL A VERTICALLY-POSITIONED LARGE-DIAMETER WELL PIPE EXTENDING DOWN THROUGH THE CENTRAL OPENING OF SAID SUPPORTED WELL BASE LOWERING SAID LARGE-DIAMETER WELL PIPE FROM SAID VESSEL AND INSERTING IT INTO THE OCEAN FLOOR SO THAT THE UPPER END OF SAID PIPE IS ADJACENT TO THE OCEAN FLOOR REDUCING THE DIAMETER OF THE CENTRAL OPENING THROUGH THE SUPPORTED WELL BASE AT THE VESSEL, DRILLING A HOLE IN THE OCEAN FLOOR THROUGH THE WALL PIPE POSITIONED THEREIN, RUNNING A STRING OF WELL CASING THROUGH THE REDUCED CENTRAL OPENING OF SAID WELL BASE OF SAID VESSEL UNTIL THE LOWER END OF SAID CASING IS IN SAID HOLE AND THE UPPER END OF SAID CASING IS AT SAID SUPPORTED WELL BASE, CONNECTING SAID WELL BASE TO THE WELL CASING NEAR THE UPPER END THEREOF, AND LOWERING SAID CASING INTO THE HOLE UNTIL THE WELL BASE CONNECTED TO SAID CASING IS POSITIONED ADJACENT THE TOP OF THE WELL PIPE SET IN THE OCEAN FLOOR. 